Porous fuel treatment element

ABSTRACT

The invention relates to a porous fuel treatment element for an evaporation burner, comprising at least one layer ( 8 ) formed by fibers ( 10 ). Said fibers ( 10 ) comprise basalt fibers.

The present invention relates to a porous fuel treatment element for anevaporation burner, having at least one tier that is formed from fibers.

Apart from atomizing burners which are likewise used to some extent,evaporation burners in which the liquid fuel is evaporated, subsequentlytreated with supplied combustion air so as to form a fuel/air mixture,and subsequently reacted in an exothermal reaction, are often used inthe case of mobile heating apparatuses that are operated using liquidfuel, such as are used in particular as stationary heaters or auxiliaryheaters in vehicles. In particular in the case of a use in vehicles, thefuel that is also utilized for operating an internal combustion engineof the vehicle, in particular for example diesel, petroleum, ethanol,and similar, is often used as the liquid fuel.

The liquid fuel in evaporation burners of this type is usually firstsupplied to a porous fuel treatment element which serves for storing,distributing, and evaporating the fuel. In particular, a plurality ofporous fuel treatment elements which, for example, are in each caseadapted to these various functions, can also be provided.

WO 2012/155897 A1 describes an evaporator assembly for an evaporationburner for a mobile heating apparatus, in which an evaporation elementhas at least one layer from a woven metal fabric from interwoven metalwires. It is furthermore described that a multi-tiered construction inwhich a layer from a woven metal fabric is combined with a further layerfrom a non-woven metal fabric is provided, for example.

It is an object of the present invention to provide an improved porousfuel treatment element, an improved evaporation burner, and an improvedheating apparatus.

The object is achieved by a porous fuel treatment element as claimed inclaim 1. Advantageous refinements are set forth in the dependent claims.

The porous fuel treatment element for an evaporation burner has at leastone tier that is formed from fibers. The fibers comprise basalt fibers.The fibers of the at least one tier herein can in particular be formedfrom basalt fibers, for example. However, it is also possible, forexample, for further fibers apart from basalt fibers to be present. Theentire fuel treatment element herein can be formed from basalt fibers,for example, or at least be formed from one or a plurality of tierswhich comprise basalt fibers. However, it is also possible, for example,for the porous fuel treatment element to additionally have also one or aplurality of tiers which do not include any basalt fibers.

As compared to the fibrous materials that are conventionally used forporous fuel treatment elements, basalt fibers have significantadvantages in this application. In comparison to glass fibers orasbestos fibers, for example, basalt fibers have superior physical,mechanical, and chemical properties in terms of a use in a porous fueltreatment element. Basalt fibers are a very strong but neverthelessflexural fibrous material which can in particular be processed in asimple manner so as to form textile planar structures such as, inparticular, a felt, a non-woven fabric, a needled mat, a scrim, a wovenfabric, a warp/weft-knitted fabric, a knitted fabric, or a braidedfabric. The material herein is in particular also suitable forevaporation burners which are conceived for very high operatingtemperatures, since basalt fibers have an extremely high resistance totemperature, in particular also when compared with conventionalmaterials such as, in particular, non-woven metal fabrics and wovenmetal fabrics. A very slight tendency towards forming deposits isfurthermore achieved, and a high storing or buffering effect,respectively, for as yet non-evaporated liquid fuel can be provided.This is furthermore a very cost-effective material that is non-hazardousin terms of health.

According to one refinement, the at least one tier has a textile planarstructure, in particular a felt, a non-woven fabric, a needled mat, ascrim, a woven fabric, a warp/weft-knitted fabric, a knitted fabric, ora braided fabric. In this case, the properties of the fuel treatmentelement can be predefined in a very targeted manner by way of theselection of the textile planar structure. Furthermore, it is alsopossible, for example, for different types of textile planar structuresto be combined with one another, for example one or a plurality of tiersfrom non-woven fabric with one or a plurality of tiers from wovenfabric, etc.

According to one refinement, the fibers of the textile planar structurehave a diameter distribution in the range between 5 μm and 35 μm. Inthis case, a very positively defined distribution of the diameter of thefibers is provided such that the properties of the fuel treatmentelement can be set in a targeted manner. Furthermore, in the case ofsuch a positively defined diameter distribution it is reliably ensuredthat no risks in terms of health are associated with the handling of thefibers.

Health hazards in the handling can be excluded in a particularlyreliable manner in particular when the fibers have a length of at least150 μm, preferably a length of at least 200 μm. The basalt fibers in thecase of the porous fuel treatment element can particularly preferably bepresent as so-called endless fibers of a very great length, which can beproduced in a known technical manner.

According to one refinement, the porous fuel treatment element can haveat least one tier from basalt wool. The aforementioned at least one tiercan in particular comprise basalt wool, or else one or a plurality offurther tiers which comprise basalt wool or are formed from basalt wool,for example, can be additionally provided. The use of basalt woolenables a particularly cost-effective production.

According to one refinement, the porous fuel treatment element has atleast one further tier formed from fibers. The fibers of the at leastone further tier can preferably also comprise basalt fibers. Aparticularly advantageous, in particular temperature-resistant, designembodiment is provided in this case. Alternatively however, it is alsopossible, for example, for the at least one further tier to compriseother fibers such as, for example, in particular metal fibers or metalwires, respectively.

According to one refinement, the fibers of the at least one tier have aglass-type amorphous structure.

According to one refinement, the fibers of the at least one tier areinterconnected by sintering. A particularly robust and dimensionallystable implementation of the fuel treatment element is enabled in thiscase, which in turn permits simple handling in the assembly of theevaporation burner. Furthermore, an additional separate supportingstructure which would cause additional costs and labour input can bedispensed with in this case.

According to one refinement, the fibers are formed by fiber bundles,multifilaments, and/or rovings.

The object is also achieved by an evaporation burner for a mobileheating apparatus operated by liquid fuel, having such a porous fueltreatment element.

The object is furthermore also achieved by a heating apparatus having anevaporation burner which has such a porous fuel treatment element.

Further advantages and refinements are derived from the descriptionhereunder of an exemplary embodiment with reference to the appendeddrawings in which:

FIG. 1 shows a schematic illustration of part of an evaporation burnerhaving a porous fuel treatment element in a mobile fuel-operated heatingapparatus according to one embodiment;

FIG. 2a ) shows a schematic illustration of an evaporator receptaclehaving a fuel treatment element according to a first modification of theembodiment;

FIG. 2b ) shows a schematic illustration of an evaporator receptaclehaving a fuel treatment element according to a second modification ofthe embodiment;

FIG. 3a ) shows a schematic illustration of an evaporator receptaclehaving a fuel treatment element according to a third modification of theembodiment;

FIG. 3b ) shows a schematic illustration of an evaporator receptaclehaving a fuel treatment element according to a fourth modification ofthe embodiment;

FIG. 3c ) shows a schematic illustration of an evaporator receptaclehaving a fuel treatment element according to a fifth modification of theembodiment;

FIG. 4 shows a view of a fuel treatment element according to a firstembodiment;

FIG. 5 shows a view of a fuel treatment element according to a secondembodiment;

FIGS. 6a )-g) show schematic illustrations of various textile planarstructures as which the fuel treatment element can be implemented;

FIG. 7 shows a schematic exploded illustration for explaining thearrangement of the fuel treatment element in an evaporator receptacle;

FIG. 8 shows a schematic exploded illustration for explaining thearrangement of the fuel treatment element in an evaporator receptacle inthe case of a modification.

EMBODIMENTS

A first embodiment will be described in more detail hereunder withreference to FIG. 1.

A region of an evaporator receptacle 2 and of a burner lid 3 of anevaporation burner 1 for a mobile heating apparatus is schematicallyillustrated in FIG. 1. FIG. 1 is a schematic illustration in a planethat includes a main axis Z of the evaporation burner. The evaporationburner can be substantially rotationally symmetrical in relation to themain axis Z, for example. The evaporation burner 1 can be configured fora vehicle heating apparatus, for example, in particular an auxiliaryheater or a stationary vehicle heater. The evaporation burner 1 hereinis configured in particular for converting a mixture of evaporated fueland combustion air, thus a fuel/air mixture, in a combustion chamber 4,while releasing heat. The conversion herein can be performed inparticular in a flame-generating combustion, but a partially or fullycatalytic conversion is also possible. The released heat in a heatexchanger (not illustrated) is transmitted to a medium to be heated,which can be formed by air or a coolant liquid, for example. Notillustrated in the schematic illustration of FIG. 1 are in particularthe heat exchanger, the discharge for the hot combustion exhaust gases,the combustion-air conveying device (for example a blower) that islikewise provided, the fuel conveying device (for example a meteringpump), the control unit for actuating the evaporation burner, etc. Thesecomponents are well-known and are described in detail in the prior art.

The evaporation burner 1 has an evaporator receptacle 2 in which aporous fuel treatment element 5 is disposed. The evaporator receptacle 2in the case of the exemplary embodiment is substantially pot-shaped. Thefuel treatment element 5 is received in the pot-type depression of theevaporator receptacle 2 and in particular can be fixedly held in thelatter, for example by welding, brazing/soldering, jamming, or with theaid of a suitable securing element. The design embodiment of the fueltreatment element 5 will be described in even more detail hereunder.

A fuel supply line 6 for supplying liquid fuel to the fuel treatmentelement 5 is provided. The fuel supply line 6 opens into the evaporatorreceptacle 2 and is connected to a fuel conveying device (notillustrated) by way of which liquid fuel in a predefined quantity can beconveyed through the fuel supply line 6, as is schematically illustratedby an arrow F. The fuel supply line 6 is fixedly connected to theevaporator receptacle 2, for example by welding or brazing/soldering.

The combustion space 4 on the circumference is delimited by a combustionchamber 7 which can be formed, for example, by a substantiallycylindrical component from a temperature-resistant steel. The combustionchamber 7 is provided with a plurality of bores 7 a by way of which thecombustion air can be supplied to the combustion space 4, as isschematically illustrated by arrows in FIG. 1. The bores 7 a herein arepart of a combustion air supply L by way of which the combustion air issupplied to a side of the fuel treatment element 5 that faces away fromthe fuel supply line 6.

The evaporation burner 1 is configured in such a manner that inoperation liquid fuel can be supplied by way of the fuel supply line 6to the fuel treatment element 5. On the one hand, on account of amultiplicity of cavities, a distribution of the fuel across the entirewidth of the fuel treatment element 5 is performed in and on the fueltreatment element 5, and an evaporation or volatization, respectively,of the fuel is performed on that side that faces the combustion space 4,on the other hand. In the case of the embodiment illustrated, the fueltreatment element 5 has a substantially circular cross-sectional shape,the main axis Z of the evaporation burner 1 running in the center ofsaid circular cross-sectional shape. However, the fuel treatment element5 can also have other cross-sectional shapes.

The combustion burner 1 is configured in such a manner that anevaporation or volatization, respectively, of the liquid fuel isperformed in the fuel treatment element 5 and on the surface of thelatter, the evaporated fuel being mixed with the supplied combustion airso as to form a fuel/air mixture only when exiting from the fueltreatment element 5, that is to say at the side of the combustion space.The supply of liquid fuel and combustion air is thus performed ondifferent sides of the fuel treatment element 5. The conversion of thefuel/air mixture in an exothermal reaction herein does not take place inthe fuel treatment element 5 but in the downstream combustion space 4.In the operation of the evaporation burner 1 there is thus liquid fueland fuel vapor in the fuel treatment element 5, and any air that ispotentially initially present is forced out of the fuel treatmentelement 5 by virtue of the evaporation or volatization process,respectively.

In the case of the exemplary embodiment schematically illustrated inFIG. 1, the fuel treatment element 5 has a construction with a pluralityof functional regions, said construction in the example specificallyillustrated being subdivided into a first region B1 and into a secondregion B2, the latter having a structure that deviates from thestructure in the first region B1.

The second region B2 in the case of the exemplary embodiment is disposedso as to face the fuel supply line 6, and the first region B1 isdisposed so as to face the combustion space 4.

In the case of the first modification of the embodiment schematicallyillustrated in FIG. 2a ), the fuel treatment element 5 does not have aplurality of different functional regions, there rather being only onefirst region B1.

In the case of the second modification of the embodiment schematicallyillustrated in FIG. 2b ), the fuel treatment element 5 has a steppeddesign with a total of three regions B1, B2, B3, and the evaporatorreceptacle 2 is configured in a corresponding manner. In such a case,the different regions B1, B2, B3 can be conceived in a targeted mannerwith a view to the various functions of the fuel treatment element 5,for example. For example, the second region B2 can be optimized forconveying fuel by way of capillary forces and for temporarily storingfuel, the third region B3 can be optimized with a view to a distributionof fuel in the transverse direction and serve for compensatingtolerances, and the first region B1 can be optimized with a view to theevaporation or volatization, respectively, of fuel. The differentregions B1, B2, B3 herein can differ from one another in particular interms of the construction, the structure, the material, and/or thethickness, etc. thereof.

Further potential design embodiments of fuel treatment element 5 havinga plurality of functional regions B1, B2, B3 are schematicallyillustrated in FIGS. 3a, 3b, and 3c . While the fuel supply line 6 andfurther components are again not illustrated in FIGS. 3a, 3b, and 3c ,it is understood that these further components are also present in thecase of each of these further modifications.

The construction of the fuel treatment element 5 as can be used in thecase of the embodiment and the modifications described above will bedescribed in more detail hereunder The design embodiment hereindescribed hereunder can be used for each one of the regions B1, B2, andB3, in particular also in those cases in which only one such region isprovided.

FIG. 4 shows a tier 8, formed from fibers 10, of a porous fuel treatmentelement 5 according to a first embodiment. The tier 8 in the case ofthis embodiment is formed from a woven fabric, the fibers 10 of thelatter comprising basalt fibers. In the case of the specific embodimentillustrated, the woven fabric herein is in particular formed by basaltfibers which are interwoven. In the case of the porous fuel treatmentelement 5 having one or a plurality of further tiers 9, said furthertiers 9 can also be formed from such a woven fabric, for example. Thefibers 10 within the tier 8 formed can also be fiber bundles, multifilaments, or rovings, respectively.

FIG. 5 shows a tier 8, formed from fibers 10, of a porous fuel treatmentelement 5 according to a second embodiment. The tier 8 in the case ofthe second embodiment is formed as a non-woven fabric which comprisesbasalt fibers. In the case of the specific embodiment illustrated, thenon-woven fabric herein is in particular formed by basalt fibers. In thecase of the porous fuel treatment element 5 having one or a plurality offurther tiers 9, said further tiers 9 can also be formed from such anon-woven fabric, for example. Furthermore, in a fuel treatment element5 it is also possible, for example, for one or a plurality of tiers fromsuch a non-woven fabric to be combined with one or a plurality of tiersfrom a woven fabric as described above.

Furthermore, in a porous fuel treatment element 5, one or a plurality oftiers can also be configured as textile planar structures such as aredescribed in general hereunder with reference to FIGS. 6a ) to 6 g). Itis to be noted herein in particular that arbitrary combinations of suchtextile planar structures can be used in a porous fuel treatmentelement.

Various implementations of the at least one tier 8 (or optionally alsoof the further tier 9, respectively) of the porous fuel treatmentelement 5 are illustrated in FIGS. 6a ) to 6 g). The variousimplementations have a common factor in that the fibers 10 in each casecomprise basalt fibers. In particular, the fibers 10 can in each case beformed by basalt fibers.

FIG. 6a ) shows a schematic illustration of a non-woven fabric as atextile planar structure for the tier 8 or 9, respectively, as has alsobeen described with reference to FIG. 5.

FIG. 6b ) shows a schematic illustration of an alternative in which thetextile planar structure for the tier 8 or 9, respectively, is formed bya felt.

FIG. 6c ) shows a schematic illustration of a textile planar structurethat is formed as woven fabric from basalt fibers for the tier 8 or 9,respectively, as has also been described with reference to FIG. 4.

FIG. 6d ) schematically shows a configuration of the tier 8 or 9,respectively, as a knitted fabric. FIG. 6e ) schematically shows aconfiguration of the tier 8 or 9, respectively, as a braided fabric.FIG. 60 schematically shows a configuration of the tier 8 or 9,respectively, as a warp/weft-knitted fabric. FIG. 6g ) schematicallyshows a configuration of the tier 8 or 9, respectively, as a scrim.

It is to be noted that the various textile planar structures that havebeen described by means of FIGS. 6a ) to 6 g) in a porous fuel treatmentelement 5 can be combined with one another in an almost arbitrarymanner. In the case of the textile planar structures described above, itis particularly advantageous for the fibers 10, that is to say thebasalt fibers in the case of the specific design embodiment, to have avery tight diameter distribution with diameters in the range between 5μm and 35 μm, and for the fibers 10 to in each case have a length ofmore than 150 μm, preferably more than 200 μm. The fibers 10 herein canparticularly preferably be embodied as so-called endless fibers, forexample. The fibers 10 herein have an amorphous glass-type structure.The surface of the fibers 10 can prefereably be treated with a sizing inproduction, so as to achieve an improved processability.

Alternatively or else additionally to the textile planar structuredescribed above, the tier 8 or 9, respectively, can also comprise basaltwool, which enables a particularly cost-effective production.

The integration of the fuel treatment element 5 described above and theat least one tier 8 or 9, respectively, which comprises basalt fibers,in an evaporator assembly of an evaporation burner 1 will be brieflydescribed hereunder with reference to the schematic explodedillustration in FIG. 7.

As is schematically illustrated in FIG. 7, the fuel treatment element 5described above is placed into the pot-type depression of the evaporatorreceptacle 2. In order for a sufficient mechanical stability to beguaranteed even at high temperatures in the long run, a supportingstructure 11 which can in particular be formed by atemperature-resistant metal mesh or metal woven fabric, for example, isattached to the fuel treatment element 5 on the side of the combustionspace. Fastening of the fuel treatment element 5 and of the supportingstructure 11 in the evaporator receptacle 2 is performed by way of amounting ring 12. The mounting ring 12 herein can be configured inparticular in a manner known per se as a circlip which is jammed orbraced, respectively, on the evaporator receptacle 2, or a connectionbetween the mounting ring 12 and the evaporator receptacle 2 can beestablished, for example, by welding or brazing/soldering. Theevaporator assembly that is formed in this manner can then be integratedin the evaporation burner 1 in a simple manner.

MODIFICATION

In the case of a modification of the embodiment described above, themechanical stability of the porous treatment element 5 is enhanced inthat the fibers 10 are interconnected by sintering. In this method, afixed connection is configured therebetween at the intersection pointsof the fibers 10. Sintering herein can be performed, for example, by wayof a purely thermal process in which the configuration of the connectionis performed only by providing an increased temperature and optionallyby additional compressing of the fibers 10. As an alternative to such apurely thermal process, it is however also possible, for example, forthe sintering process to be facilitated by chemical processes in thatadditional binding agents/sintering additives are applied to the fibers.

As is schematically illustrated in FIG. 8, an enhanced mechanicalstability of the fuel treatment element 5 is achieved by way of thismodification, such that the additional supporting structure 11 can bedispensed with in the construction of the evaporator assembly.

1. A porous fuel treatment element for an evaporation burner, having: atleast one tier that is formed from fibers, wherein the fibers comprisebasalt fibers.
 2. The porous fuel treatment element as claimed in claim1, wherein the at least one tier has a textile planar structure.
 3. Theporous fuel treatment element as claimed in claim 2, wherein the textileplanar structure is a felt, a non-woven fabric, a needled mat, a scrim,a woven fabric, a warp/weft-knitted fabric, a knitted fabric, or abraided fabric.
 4. The porous fuel treatment element as claimed in claim1 wherein the fibers of the textile planar structure have a diameterdistribution in the range between 5 μm and 35 μm.
 5. The porous fueltreatment element as claimed in claim 1, wherein the fibers have alength of at least 150 μm.
 6. The porous fuel treatment element asclaimed in claim 1, wherein the porous fuel treatment element has atleast one tier comprised of basalt wool.
 7. The porous fuel treatmentelement as claimed in claim 1, having at least one further tier formedfrom fibers.
 8. The porous fuel treatment element as claimed in claim 7,wherein the fibers of the at least one further tier also comprise basaltfibers.
 9. The porous fuel treatment element as claimed in claim 1,wherein the fibers have a glass-type amorphous structure.
 10. The porousfuel treatment element as claimed in claim 1, wherein the fibers of theat least one tier are interconnected by sintering.
 11. The porous fueltreatment element as claimed in claim 1, wherein the fibers are formedby fiber bundles, multifilaments, or rovings.
 12. An evaporation burnerfor a mobile heating apparatus operated by liquid fuel, having a porousfuel treatment element as claimed in claim
 1. 13. A heating apparatushaving an evaporation burner which has a porous fuel treatment elementas claimed in claim
 1. 14. The porous fuel treatment element as claimedin claim 1, wherein the fibers have a length of at least 200 μm.